Mass and/or heat exchangers which contain a multiplicity of capillaries are as a rule constructed in such a way that the ends of the capillaries are embedded in a casting composition. The capillaries with the casting composition are arranged in a housing in such a way that the casting composition represents a liquid-tight isolation between the lumen of the capillaries and the space outside the capillaries.
In mass and/or heat exchangers the capillary ends are usually embedded into the housing pipe, surrounding them, in a liquid-tight and pressure-resistant manner by means of a reactive resin or a thermoplastic polymer. These mass and/or heat exchangers are also called modules.
Especially in the case of modules having relatively large housing diameters (diameters of about 50 mm and higher), a capillary bundle firmly cast into the housing frequently causes tearing-off phenomena and leakages.
Extreme operating conditions (steam sterilization, temperature fluctuations, differential pressures between the spaces outside and inside the capillaries) and specific membrane properties (shrinkage, extension when wet) build up such high marginal stresses between the capillary casting and the housing that a secure joint, based on the adhesive strength of the casting, is not ensured.
Even clamped flange joints, in which a partially elastic casting material (for example polyurethane) is stressed between two metal flanges, do not solve the problem. Due to the cold-flow behavior of the elastic casting material, such a joint easily leads to leakages, particularly under thermal stress.